1. Field of the Invention
The present invention relates to a rotating electrical machine such as a motor or a generator or the like.
2. Description of Related Art
In recent years worldwide efforts for reducing greenhouse gases and saving energy have been made, leading to a rapid progress in the implementation of electrically powered automobiles. There are severe constraints upon the space available for installing an in-vehicle electric motor (rotating electrical machine), and moreover it is required to obtain high output with a limited battery voltage. As one means for satisfying demands for compactness together with high output for an electric motor, an electric motor employing a concentrated winding for the stator core can be used, in which thick coil wires are densely wound on divided cores of the stator, resulting in a high space factor for the stator coils.
On the other hand, as one example of counter measures for lowering the motor cost with the prior art, continuous winding of coils for a plurality of stator slots has been adopted, by which the number of connection points can be reduced and thus the assembly work has been simplified. When continuous winding is not employed, then lead wires are brought out from each coil in each slot, and the same number of connections must be made as the number of lead wires. Additionally, as such connections are done while the coils are being installed in the slots and a connection wiring plate is used for these connections, the work amount and the cost for an electric motor are pushed up due to the labor of establishing these connections.
If the coils are wound as a continuous winding, according to the structure of the coils, sometimes the connections of neutral points are done on the crossover wires. In such a case, the ease of assembly is highly hindered, if no suitable connection method is employed for the neutral point connection. In Japanese Laid-Open Patent Publication 2003-189525, a stator core is described in which a plurality of coils are wound as a four-in-parallel Y connected winding, with coils of each different phase being wound continuously (with one coil in every other slot). Since, when the stator coil is assembled with this method, portions of the crossover wires where the neutral points of two of the three phases overlap appear at three locations, accordingly a method is described for creating a neutral point for all of the three phases by establishing connections to these three portions, and by connecting these three locations together using connecting wires. However with this method, since fused connections need to be provided at the three locations in the state in which the stator coil is already installed upon the stator core, accordingly the efficiency of the assembly task is bad, and this causes increase of the man-hours required for assembly. Furthermore, since the lead wires of the coils that are connected as four-in-parallel in a Y-connection pattern and the respective lead wires of the 3 phases are far separated from each other, accordingly a connection wiring plate needs to be used with this method, and this causes the cost of the motor to become higher.
A continuous winding for a divided core of a motor with a concentrated winding is disclosed in Japanese Laid-Open Patent Publication 2006-50690. Here, the coils of same phase of a stator coil for 14 poles and 12 slots are wound as four continuous windings, and constitute a stator coil wound with 2-in-series 2-in-parallel Y connected wiring. Furthermore, by the four continuously wound coils, which are all wound in same direction, for one of the U phase, the V phase, and the W phase, the locations of lead wires for each phase and the locations of neutral point connections for each phase are respectively gathered at positions opposite to each other on the circumference of the stator. With the construction disclosed in Japanese Laid-Open Patent Publication 2006-50690, it is possible to reduce the number of neutral point connection points, but a connection wiring plate is still necessary for connecting together the three neutral points with the method described there, since the neutral points of the U phase coil, the V phase coil, and the W phase coil are still located at different positions.